Converter



Jan. 24, 1933. l. HECHENBLEIKNER ET AL 1,894,992

CONVERTER Filed Feb. 6. 1950 INVENTORS INGENUIN HECHENBLEIKNER NICOLAY T|TLE5TAD Wfl #M ATTORNEY5 Patented Jan. 24, 1933 a UNITED STATES PATENT oFricEg V'INGENUIN HECHENBLEIRNER'ANE NICOLAY TITLEsTAn, OE CHARLOTTE, VNORTH cARoLINA,4 AssIGNORs, EY IvrEsNE AssIoNi/IENTS, To CHEMICAL CONSTRUCTION CORPORATION, or CHARLOTTE, NORTH CAROLINA, A CORPORATION 0E DELAWARE CONVERTER Application filed February 6, 1930. Serial No. 426,269.

vThis invention relates to converters, and more particularly -to converters yemploying a gauze catalyst. f

The general Object of the present invention is to increase the operating life, `to increase the conversion `eiiiciency, and to decrease the catalyst cost for a given quantity of conversion product, when using a gauze catalyst. i n.

Our invention is particularly, applicable to and therefore will be described in connec tion withv the manufacture of nitric acid. Inv

this process ammonia is distilled from ammonia liquor by a current of air, and the ammonia and air mixture is passed through a converter utilizing platinum gauze as a catalyst in order to oxidize the ammonia. One primary object of the present invention is to obtain maximumoperating efficiency in the entire manufacturing plant. This we have found may in general be .obtained by utilizing appropriately large units in the plant. M Y

LThe platinum gauze ,in ythe converter is ordinarily in the form of a cylindrical basket through which the reaction gas is forced. Upon increasing the size of the various units used throughout the plant it heretofore was the practice to also commensurately increase the size of the converter and of the platinum gauze basket ,used therein. This has resulted -in an increased catalyst cost principally due to the fact that greater diiiiculty is experienced with the gauze, it blowing through or bursting in considerably less time than is the case with smaller baskets. This difficulty has militated against the otherwise desirable use of large units throughout the plant, and, accordingly, one important object of our invention is to overcome this diiiculty and to reduce the catalyst cost per ton of acid, while retaining the optimum size of units for the various steps in the manufacturing process. To this end we employ a multiple converter consisting essentially of a plurality of relatively small gauze catalyst ,converters of the basket type,

and means to feedreaction gas thereto in parallel. t i

Another object of the present invention is to Obtain a high conversion efliciency as kwell y t It is obvious that the conversion eiiiciency may be greatly reducedV as a low catalyst cost.

if the reaction gas is fed to a relatively exhausted catalyst, and, in accordance with a further feature of our invention, thereaction gas is suitably apportioned amongst the gauze baskets for best conversion eiiiciency, the flow of gas to an exhausted basket being reduced relative to that througha basket which is still in active condition.`

To the accomplishment of the foregoingy and such other objects as will hereinafter appear, our invention consists in the elements and their relation one to the other, as hereinafter more particularly described and sought to be defined in the claims; referencebeing had to the accompanying drawing kwhich shows the preferred embodiments of ourin vention, and in which Fig. l is a section taken in `elevation through a multiple converter embodying our invention; and

Fig. 2 is a horizontal section taken in the plane of the line 2 2 in Fig. l.

In the manufacture of nitric acid by the ammonia oxidation process, ammonia liquor is fed to a stripping column or tower through which a current of air is blown, and the resulting mixture of air and volatilized or distilled ammonia is led to a converter Where the ammonia is oxidized. The converter employs platinum gauze as a catalyst and this gauze isusually in the form of a cylindrical basket. The oxidized gas or reaction product from the converter may be absorbed `in suitable absorption tanks or drums to obtain the desired nitric acid. A compressor may be used in the flow circuit in Order to decrease the pressure in the stripping tower to aid' the volatilization of the ammonia and to increase the pressure in the absorption drums to aid in the solution ofthe acid and anhydride. Suitable heat exchangesmay be used in Various combinations in the system in order to take advantage of the thermal nature ofthe veo asithestrippingtower, the ammonia liquor tanks, thevair blower, ythe absorption 'drums been the practice to commensurately.increase the sizeof the converter used in order to obtain the necessary area of platinum gauze catalyst. .The platinumbecomes increasingly brittle with use, Vand after a time the strength of thel platinum Wire in the gauze seems Vto become exhausted and the gauze VVbursts under the'pressure differential to which it isexertedby the reaction gas lowing therethrough. It is found that the bursting point is, reached much sooner With a large converter than with a small converter.. For example, in convert-ing a certain amount of `rammonia perisquare inch of contactsurface,

a-platinumfgauze of say fourinches diameter will lasttvvelve months or more; one of six i inches diameter Willlast say eight to ten` months; 'one of eight inches diameter Will .last say six to eight months; While a gauze vwhich is fourteen inches in diameter Will last only from three to five months. Y It should beunderstood of the gauze is premature and is not due to exhaustion of the catalytic liie of they platinum. For example, the Wire from the bursty gauze'may be revveaved and reworked, but this" procedure is expensive and, consequentthe use of a large converter greatlyincreases the catalyst cost per ton of acid manuactured. Y y

In accordance with our invention We emplo instead of a simple large converter, a mu 'tiple converter. We utilize appropriately large units in the plant for efficiently practicing the successive steps in the process 'other than the conversion step, and We subdivide the necessary gauze areafor the conf version step into a Vplurality of relatively small converters to which Vive-feed the relaction' 'gas in parallel. In its apparatus laspect our invention resides in the provision ofa novel multiple converter, a `preferred form of which may bestrbe understood by reference to the accompanyingdravving.

In the multiple converter shown the con- V4version chamber is subdivided into aA plurality of relatively small conversion cham- .bers C, in each of ,which a. platinumv gauze basket Pis suspended,preferably` from a nickel holder H at the top of the conversion `chambers C. A common gas inlet I is used to supply reactionv gas to the platinum baskets 'P, Vwhile a common gas outlet OV discharges* the reactionproduct from t-he several con- 65. version chambers."

,and heat exchangers,it has heretofore alsoy that the bursting Considering the converter in greater detail, each platinum gauze P is preferablyin the form-of a basket having a cylindrical sur-V face 2 and a bottom surface 4. The bottom gauzeV is coveredy with asi'lica disk 6 in order toprevent im urity-containing dust in they f reaction gas rom settlingfon and eating through the bottom gauze ,4. The cylindri, calfgauze surface 2 is preferablyv composed of a plurality, sayfour layers, 'of' latinum mesh gauze,"and these layers may, i desired,

be varied in mesh and Weightof Wire in ac.-

cordance with the disclosure in a copending application: ofrfNicolay Titlestad and Sam- 'cordance with our .copending application Serial No. 431,176, iiled February A25, 1930;

It will thusrbe'seen that each of the small converters in our multiple' converter` is' similar tothe large lconverters heretofore used. AV 'similar converter lining, v indicated. at 12, may be employed, but this is so disposed with-Lv in the multiplefconverter shell 14 asvto form 'a plurality of small chambers C, as is best indicated in` Fig. 2. These small chambers all lead into a common large chamber 16nea'r the bottom of the converter, and this is in direct communication'with the outlet O. 'i

A The converter lining 12 and shell 14 should kbe provided with :sight or peep holes 18, the

outer extremities of which are provided with a heat resistant glass '20, suchr as yrex, in order to permity of yins ection oft e conditionof'the fcatalyst bas ets. d

Reaction gas is fed through the inlet I and is distributed to the yvarious holders 'H by means of acommon hood 22 made of `a vsuitable metal, say aluminum. The reaction at this time is cool and no lining is needls. The entire converter chamber beyond the catalyst Vand including the Voutlet O should be suitably linedV `vith a're'fractory lining because of the high temperature of the reactiony product after conversion. e

Asingle gas-tight shell or housing is used,

f and outsidel connectionfneed be made to only a single inlet and a single outlet,'all as con- Akveniently asV 'if a single large kconverterY were being used. `But the inside is subdivided into plural compartments, best formed'simplyby a solid filling of lining material. Each com-y Y Apartment is preferably generally cylindrical,

as shown, and has its gauzefbasket mounted concentricaly therein, as shown, so thaty the effective gauze surface iseverywheree u1-y distant fromthe nearest 'lining surface. V fhe arrangement reduces space requirement and A.gas leaks, and kconserves heat..

By the expediente already briefly mentioned in describing the catalyst baskets, the life thereof has been lengthened until the limiting factor is bursting or blowing through of the cylindrical portion 2 thereof. The greatly reduced life of the large baskets we believe to be due to the increased tension under which the gauze is placed when the diameter of the basket is increased, inasmuch as the area upon which the pressure differential of the gas flowing through the gauze is exerted is correspondingly increased. We therefore propose'to limit the diameter of the gauze baskets` thereby limiting the stress applied theretol and permitting the useful life of the basket to more nearly approach the chemically or catalytically active life of the platinum. Of course, the area of catalyst must be maintained in order to retain the desired conversion efficiency. It is not desir-k able to simply reduce the diameter and increase the length of the basket because the conversion efficiency seems to be dependent upon the ratio of the basket diameter and length. In, accordance with our invention the multiple converter already described is employed and the total area of the gauze baskets is made equal to that desired, the proportioning of the individual baskets may be selected as desired, and the size of the individual baskets, and particularly the diameter thereof, may be limited to any desired value. It goes without saying that while the multiple converter illustrated employs four baskets, this quantity may be varied as .desired to suit the 'requirements ofany particular case. It will also be appreciated that while we think it preferable to have the converter chambers separated with insulating material as shown, this is not at all essential to the practice of the invention, for separate baskets may be used all mounted in a single large converter chamberf The multiple converter reduces the catalyst cost per ton of acid manufactured by lengthening the useful life of the gauze catalyst. It is additionally necessary to obtain a high conversion efhciency, and some of the factors affecting this have already been mentioned. @ne additional factor remains to be considered, which is caused by the fact that the baskets may deteriorate or wear at different rates. For example, suppose one of the baskets is nearly exhausted while the others continue to be active. If reaction gas is fed to all of the baskets equally the overall conversion efficiency willimmediately be reduced because of the effect of the nearly exhausted gauze. To maintain the conversion efficiency it is necessary to appropriately vary or apportion the feed of reaction gas to the several ganzes, the feed to a more nearly exhausted gauze or basket being reduced relative to that to the more active gauzes or baskets.

This apportionment maybe obtainedby having separate pipes or inlets leading to the various gauzes and all extending from a common manifold or header,fwith independent valves or dampers in each of the pipes or inlets to apportion the flow of reaction gas. However, we have found that in the ordinary case this precaution Vis superfluous, and a simple valveless arrangement such as we have illustratedmay be employed to good advan- Vtagebecause there is an automatic apportionment or distribution of the reaction gas. More specifically, We have found thatwhen the life of platinum gauze approaches eX- haustion thepressure drop therethrough increases. This has the effect of retarding the gas flow through such a gauze, and of correspondingly increasing the proportion of flow through the gauzes which are in better or more active condition. The overall effect of this phenomenon is that in the multiple converter the load through the various gauzes is automatically equalized and appropriately varied if some of the baskets should approach exhaustion sooner thanothers. In this manner the conversion efliciency of the multiple converter is kept at a high value.

A The preferred mode of successfully practicing our invention and of constructing the apparatus for the same, as well as the many advantages thereof, are believed to be apparent from the foregoing description. The eiiciency of a plant which practices a process including catalytic conversion yof reaction gas by means of a gauze catalyst, iskept high'by utilizing appropriately large units for efficiently practicing the successive steps in the process other than the conversion step.

Meanwhile, the catalyst cost is kept low by subdividing the necessary gauze area into a plurality of relatively small converters. The conversion efficiency of the multiple converter is kept high by adopting for each of the small converters the precautions ordinarily taken'with a single large converter, and fur ther by the preferably automatic apportionment or distribution of the load on the in- -dividual small converters making up the multiple converter.

It will be appreciated that our invention is applicable to processes other than the manufacture of nitric acid and ammonia oxidation, and to catalysts other than platinum and a the platinum alloys, so long as the catalyst is in the form ofv a meshl or gauze or any like screen through which reaction fluid is passed.

It will be apparent that while we have shown and described our invention in the preferred forms, many changes and modiications may be made in the method and structures disclosed without departing from the spirit of the invention, defined in the following claims.

We claim:

l. A catalytic converter comprising a relaf chambers.`

tively large converter shell or housing,- a plurality of gauze baskets supported in said converter. housing and arranged to collectively receive the `full gasilow and to operate thereon in parallel, the'length andthe diameter of each of said gauze-baskets being made in optimum ratio for `best gas flow distribution and maximum conversion efficiency, -a common gasinlet .to theY converter housing, and a common 'Uasoutlet for discharging there- Y action productsfrom the conversion Vcham-V c bers. l

- 2. A converter for the catalytic oxidation of ammonia, comprising arelatively large converter shell orV housingv subdivided by a filling of lining material into a plurality of conversion chambers, Va platinumv gauze basket supported in each of the said conversion chambers, a common gas inlet to the converter housing, and a common gas outlet for discharging the reaction products from the conversion chambers. v f

3. A converter forV the catalytic oxidation of ammonia, comprising a relatively large converter shell or housing subdivided by a filling of lining material into a plurality of conversion chambers, a platinum gauze basket supported in each of the said conversion chambers, the length and the diameter of Yeachof said gauze baskets' being made in optimumratio for best gas flow distribution and maximumy conversion eiiiciency, a commongas inlet to the Vconverter shell or hous-` ing, and acommon gas outlet for discharging the reaction products from the conversion 4. A converter for the catalytic oxidation Vof ammonia, comprising a relatively large converter shell or housing subdivided by a filling of lining material into a plurality of generally ,cylindrical conversion chambers, aplatinuin gauze basket concentrically supported in 4each of thesaid conversion chambers so4 that the effective gauze larea is equidistant from the lining Walls, the length and the diameter of each of .said gauze baskets being made iny optimum ratio for best gas flow distribution and maximum lconversion eiiiciency, a common gas inlet to the converter shell or housing, and a common gas'outlet for discharging the reaction products from the conversion chambers.

Signed at YCharlotte Y Mecklenburgand State of North Carolina this 3 day of Feb. Afl). 1930.

INGENUIN HisCHENBLEiKNER.V NIcoLAY TITLESTAD.

in the ,countyy of Y 

